JP7113571B1 - flexible flat cable - Google Patents

Abstract

A flexible flat cable that has excellent high-frequency characteristics, can transmit signals at high speed with low loss, is easy to handle, and is advantageous in terms of cost. A flexible flat cable in which a plurality of conductors are arranged in parallel at predetermined intervals inside a covering material made of a tape-shaped insulator, wherein the insulator is composed of polyolefin resin and heavy calcium carbonate powder. It is characterized by containing at a mass ratio of 50:50 to 10:90, and having a dielectric constant ε of 5 or less at a frequency of 1 GHz or higher and a temperature of 25 ° C., and a dielectric loss tangent tan δ of 5 × 10-4 or less. flexible flat cable. [Selection drawing] Fig. 1

Description

The present invention relates to flexible flat cables. More specifically, the present invention relates to a flexible flat cable having a tape-shaped insulator in which polyolefin resin is highly filled with heavy calcium carbonate as a covering material.

A flexible flat cable is widely used as a wiring material, especially as an internal wiring material for electronic equipment, because it is space-saving and enables high-density wiring. A flexible flat cable (hereinafter sometimes abbreviated as "FFC") consists of a tape-shaped insulator (base film) with multiple rectangular or linear conductors in the width direction, usually insulating. Wiring members are arranged in a plane in parallel at predetermined intervals with an adhesive interposed therebetween. Since FFC also has the advantage of being thin and excellent in flexibility, it is useful as various wiring materials such as connection between substrates of electronic equipment and home electric appliances, roofs, doors, floors, instrument panels of automobiles, and the like.

Insulators in FFC include polyester resins such as polyethylene terephthalate (PET), polyamide resins, general-purpose polyolefin resins, (meth)acrylic resins, polyarylates, polyimides, polycarbonates, polyethersulfones, polyphenylene sulfides, Resins such as polyether sulfide, polyether ether ketone, and fluorine resin are used, and PET is particularly frequently used (Patent Documents 1 to 3, Non-Patent Document 1). As the adhesive, a polyester-based adhesive, a polyamide-based adhesive, a polyurethane-based adhesive, a modified polyolefin-based adhesive such as maleic anhydride-modified polypropylene, an epoxy resin, or the like is used (Patent Document 1, Non-Patent Document 1 ). In addition, in order to make the FFC flame retardant, metal hydrates such as magnesium hydroxide, aluminum hydroxide, and titanium dioxide, phosphorus compounds such as antimony trioxide and triphenyl phosphate, and zinc borate are added to the adhesive. Borates, bromine compounds such as decabromodiphenyl oxide, and the like are optionally added.

JP 2008-218252 A JP 2011-187388 A JP 2012-234739 A

Fukuda, Nishikawa, Hayami, Katsumata, Matsuda: SEI Technical Review No. 186, pp. 13-16 (2015)

In recent years, the number of electronic devices that process a large amount of information at high speed has increased, and the need for FFC that can transmit signals at high speed with low loss is increasing. In order to increase the amount of information to be transmitted, it is necessary to increase the frequency of the circuit, but as the frequency increases, the transmission loss tends to increase as well. Resins having polar groups, such as PET and polyamide, described in Patent Documents 1 to 3 generally have a large dielectric loss. Therefore, an FFC having such a resin as an insulator is inferior in high-frequency characteristics, and may cause transmission loss, transmission delay, and the like. Polyolefin-based resins have a smaller dielectric loss than PET and the like, but are required to further improve high-frequency characteristics and the like as coating materials for FFCs. Polyolefin-based resins also have the drawback of poor flame retardancy, so they are not often used as insulators for FFCs. In addition, the FFC using polyimide or fluororesin as an insulator is often hard and inferior in handleability, and also has a cost problem. As described above, the conventional FFC has problems in actual use as an FFC for high-speed, large-capacity communication.

The present invention has been made in view of the above circumstances, and provides a flexible flat cable that has excellent high-frequency characteristics, can transmit signals at high speed with low loss, is easy to handle, and is advantageous in terms of cost. The task is to

As a result of extensive studies, the inventors of the present invention have found that in a flexible flat cable in which a plurality of conductors are arranged in parallel at predetermined intervals inside a covering material made of a tape-shaped insulator, the insulator is made of a specific material and characteristics. It was found that by using a material, high-frequency characteristics are improved, signals can be transmitted at high speed with low loss, and an FFC that is easy to handle, has excellent mechanical characteristics, and is advantageous in terms of cost can be obtained. rice field.

That is, the present invention for solving the above problems is a flexible flat cable in which a plurality of conductors are arranged in parallel at predetermined intervals inside a coating material made of a tape-shaped insulator,
The insulator contains polyolefin resin and heavy calcium carbonate powder at a mass ratio of 50:50 to 10:90, and has a relative dielectric constant ε of 5 or less at a frequency of 1 GHz or higher and a temperature of 25 ° C. A flexible flat cable (FCC) characterized by having a dielectric loss tangent tan δ of 5×10 ⁻⁴ or less.

One embodiment of the FFC of the present invention provides a flexible flat cable, wherein the polyolefin-based resin is a polypropylene-based resin and/or a polyethylene-based resin.

In one embodiment of the FFC of the present invention, a flexible flat cable is presented wherein said ground calcium carbonate powder is surface-treated ground calcium carbonate powder.

In one embodiment of the FFC of the present invention, the heavy calcium carbonate powder has an average particle size of 0.7 μm or more and 7.0 μm or less by an air permeation method according to JIS M-8511. be

In one embodiment of the FFC of the present invention, the heavy calcium carbonate powder has a BET specific surface area of 0.1 m ² /g or more and 10.0 m ² /g or less, and a circularity of 0.50 or more and 0.95 or less. A flexible flat cable is shown.

In one embodiment of the FFC of the present invention, the heavy calcium carbonate powder contains at least two groups of particles having different average particle sizes, and the at least two groups of particles having different average particle sizes are defined by JIS A primary calcium carbonate particle group having an average particle size of 0.7 μm or more and less than 2.2 μm by an air permeation method according to M-8511, and an average particle size of 2.2 μm or more by an air permeation method according to JIS M-8511. A flexible flat cable containing secondary calcium carbonate particles of 7.0 μm or less in a mass ratio of 1:1 to 5:1.

In one embodiment of the FFC of the present invention, when the average particle size of the first calcium carbonate particle group is a and the average particle size of the second calcium carbonate particle group is b, the a/b ratio is 0 A flexible flat cable is shown that is less than 0.85.

In one embodiment of the FFC of the present invention, a flexible flat cable is shown in which the porosity of the insulator is 5% or more and 35% or less.

The flexible flat cable of the present invention has excellent high-frequency characteristics and can transmit signals at high speed with low loss. The flexible flat cable of the present invention is also easy to handle, has excellent mechanical properties, and is advantageous in terms of cost.

It is a schematic diagram showing one embodiment of the flexible flat cable of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram which shows one Embodiment of the flexible flat cable of this invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on embodiments, but the present invention is not limited to these embodiments.

[Flexible flat cable]
The flexible flat cable of the present invention is a flexible flat cable in which a plurality of conductors are arranged in parallel at predetermined intervals inside a coating material made of a tape-shaped insulator, wherein the insulator is composed of polyolefin resin and heavy carbon dioxide. and calcium powder at a mass ratio of 50:50 to 10:90, and at a frequency of 1 GHz or higher and at a temperature of 25 ° C., the dielectric constant ε is 5 or less and the dielectric loss tangent tan δ is 5 × 10 ^-4 or less. It is characterized by The members constituting the flexible flat cable of the present invention are described below.

1 and 2 are schematic diagrams and cross-sectional schematic diagrams showing an embodiment of the flexible flat cable of the present invention. In the flexible flat cable 1, a plurality of conductors 13 are arranged in parallel at predetermined intervals between tape-like covering materials 11 and 12 made of an insulating material with an adhesive layer 14 interposed therebetween. Here, the cross-sectional shape of the flexible flat cable 1 and the conductor 13 is not particularly limited, and may be an elliptical shape or an elliptical shape in addition to the rectangular shape shown in FIG. The flexible flat cable of the present invention is not limited to the structure shown in FIGS. can also

In the FFC of the present invention, the type of conductor is not particularly limited, and various commonly used conductors can be used depending on the purpose. For example, prismatic or cylindrical conducting wires made of various metals such as copper, copper alloys, aluminum, nickel, gold, silver, and various solders may be used, and the structure is obtained by twisting these conducting wires. good too. Also, multiple types of conductors with different cross-sectional shapes, sizes, materials, etc. can be used.

In the embodiment shown in FIG. 2, the material of the adhesive layer 14 is also not particularly limited. From the viewpoint of enhancing the high-frequency characteristics of the FFC, it is preferable to select an appropriate adhesive (selection of the adhesive will be described later). brought.

≪Insulator≫
The flexible flat cable of the present invention is characterized in that the insulator contains polyolefin resin and heavy calcium carbonate powder at a mass ratio of 50:50 to 10:90, and has a frequency of 1 GHz or higher and a temperature of 25 ° C. and a dielectric constant ε of 5 or less and a dielectric loss tangent tan δ of 5×10 ⁻⁴ or less. Conventional FFCs using PET or polyamide resin as an insulator, and FFCs using a polyolefin resin that does not contain heavy calcium carbonate powder as an insulator may cause poor transmission in high-speed, large-capacity communication. On the other hand, the FFC of the present invention composed of the insulator as described above has excellent high-frequency characteristics, and can transmit signals at high speed with low loss. The polyolefin resin and heavy calcium carbonate powder contained in the insulator are described below.

<Polyolefin resin>
In the flexible flat cable according to the present invention, the polyolefin resin that can be used as the insulator is not particularly limited, and various resins can be used according to the application, function, etc. of the FFC. Polyolefin-based resin is a resin mainly composed of olefin component units, and specifically includes polypropylene-based resin, polyethylene-based resin, polymethyl-1-pentene, cyclic olefin polymer, ethylene-cyclic olefin copolymer, and the like. polyolefin resin; ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid copolymer metal salt (ionomer), ethylene-acrylic acid alkyl ester copolymer Polymers, ethylene-methacrylic acid alkyl ester copolymers, functional group-containing polyolefin resins such as maleic acid-modified polyethylene and maleic acid-modified polypropylene, and mixtures of two or more of these may be used.

Here, the phrase “mainly composed of” olefin component units means that the olefin component units are contained in the polyolefin resin in an amount of 50% by mass or more, and the content is preferably 75% by mass or more. It is preferably 85% by mass or more, more preferably 90% by mass or more. In particular, resins in which substantially all of the monomer components are olefins, especially polyolefin homopolymers (homopolymers) are preferred. Such polyolefin resins have a dielectric constant of generally 3 or less, particularly 2.5 or less, for example, in the range of 2.0 to 2.3. It is suitable as an insulator material having a tangent tan δ of 5×10 ⁻⁴ or less. The method for producing the polyolefin resin used in the present invention is not particularly limited, and can be obtained by any method using a radical initiator such as a Ziegler-Natta catalyst, a metallocene catalyst, oxygen, or a peroxide. It may be something else.

Examples of the polypropylene-based resin include resins having a propylene component unit of 50% by mass or more, and examples thereof include propylene homopolymers and copolymers of propylene and other copolymerizable monomers. Propylene homopolymers include isotactic, syndiotactic, atactic, hemiisotactic, and linear or branched polypropylenes exhibiting various stereoregularities. The above copolymer may be a random copolymer or a block copolymer, and may be a terpolymer as well as a binary copolymer. Copolymerization components (other monomers) include, but are not limited to, tetrafluoroethylene, vinyl acetate, and the like. In the present invention, it is preferable to use a homopolymer or a resin copolymerized with a small amount of another monomer, for example, less than 5% by weight. It should be noted that even in propylene homopolymers, as a result of polymerization, there are cases where a structure as if an α-olefin such as hexene is copolymerized is partly included, but in the present invention, such a polymer is also included. , is broadly included as a propylene homopolymer (propylene homopolymer). Moreover, these polypropylene resins can be used individually or in mixture of 2 or more types.

Examples of the polyethylene-based resin include resins having an ethylene component unit of 50% by mass or more. Examples include high-density polyethylene (HDPE), low-density polyethylene (LDPE), medium-density polyethylene, and linear low-density polyethylene (LLDPE). , ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-propylene-butene 1 copolymer, ethylene-butene 1 copolymer, ethylene-hexene 1 copolymer, ethylene-4-methylpentene 1 copolymer Coalescing, ethylene-octene 1 copolymer, etc., and mixtures of two or more thereof.

Among the polyolefin resins described above, polypropylene resins and/or polyethylene resins, particularly polypropylene resins, are preferably used because of their particularly excellent balance between mechanical properties and heat resistance. Among them, propylene homopolymer is preferred. As described above, the propylene homopolymer may be linear or branched polypropylene having various steric structures, and its molecular weight is not particularly limited. Propylene homopolymer, particularly isotactic polypropylene, is a thermoplastic resin having a low dielectric constant and dielectric loss tangent among various polymer materials, and is suitable for the insulator constituting the present invention. A plurality of propylene homopolymers having different steric structures and molecular weights can be used together.

The insulator constituting the present invention may further contain other resin components in addition to the above polyolefin resin. Thermoplastic resins such as poly (meth) acrylic acid (ester), polyvinyl acetate, polyacrylonitrile, polystyrene, ABS resin, polycarbonate, polyamide, polyvinyl alcohol, petroleum hydrocarbon resin, coumarone-indene resin; Elastomers such as butadiene copolymers, styrene-isoprene copolymers, styrene-butadiene-ethylene copolymers, styrene-isoprene-ethylene copolymers, acrylonitrile-butadiene copolymers, fluorine-based elastomers, etc., may be mentioned. Not limited. By blending these resin components, each component can be more uniformly dispersed in the resin composition constituting the insulator, and physical properties and workability can be improved. However, considering the compatibility of various resin components, etc., the thermoplastic resin in the insulator constituting the present invention is preferably 90% by mass or more, more preferably 97% by mass or more, and particularly preferably substantially the entire amount of the above-mentioned of polyolefin resin. If the insulator does not substantially contain resin components other than polyolefin resin, it is particularly easy to select raw materials, compositions, and processing conditions.

<Heavy calcium carbonate powder>
The insulator in the flexible flat cable according to the present invention contains a large amount of heavy calcium carbonate powder. Here, heavy calcium carbonate is obtained by mechanically pulverizing and processing natural limestone or the like, and is clearly distinguished from synthetic calcium carbonate produced by chemical precipitation reaction or the like. The pulverization method includes a dry method and a wet method, and the dry method is preferred.

The heavy calcium carbonate powder, for example, differs from the synthetic light calcium carbonate in that it is characterized by surface irregularities and a large specific surface area due to the fact that the particles are formed by pulverization. Since the heavy calcium carbonate powder has such an irregular shape and a large specific surface area, when blended in a polyolefin resin, the heavy calcium carbonate powder forms a larger contact interface with the polyolefin resin. It has an effect on uniform dispersion.

In order to enhance the dispersibility or reactivity of the heavy calcium carbonate powder, the surface may be surface-modified by a conventional method. Examples of surface modification methods include physical methods such as plasma treatment, and chemical surface treatment using a coupling agent or surfactant. Examples of coupling agents include silane coupling agents and titanium coupling agents. Surfactants may be anionic, cationic, nonionic or amphoteric, and examples thereof include higher fatty acids, higher fatty acid esters, higher fatty acid amides and higher fatty acid salts. On the contrary, it may contain heavy calcium carbonate powder that is not surface-treated.

Although not particularly limited, the heavy calcium carbonate powder preferably has a BET specific surface area of 0.1 m ² /g or more and 10.0 m ² /g or less. When the specific surface area is within this range, the resulting insulator tends to be less susceptible to workability deterioration.

In addition, the amorphousness of the heavy calcium carbonate powder (particles) can be expressed by a low degree of spheroidization of the particle shape, and is not particularly limited. It is 0.50 or more and 0.95 or less, more preferably 0.55 or more and 0.93 or less, and still more preferably 0.60 or more and 0.90 or less. If the roundness of the heavy calcium carbonate powder is within this range, the strength and moldability of the insulator will be moderate. Here, the circularity can be expressed by (the projected area of the grain)/(the area of the circle having the same circumferential length as the projected circumferential length of the grain). The method for measuring the roundness is not particularly limited, and for example, the projected area and the projected peripheral length of the grain may be measured from a micrograph, or image analysis software that is generally commercially available may be used.

The heavy calcium carbonate powder is not particularly limited, but preferably has an average particle size of 0.7 μm or more and 7.0 μm or less, more preferably 0.8 μm or more and 6.0 μm or less, and further preferably, It is 1.0 μm or more and 4.0 μm or less. The average particle size of the heavy calcium carbonate powder described in this specification is a value calculated from the results of measuring the specific surface area by an air permeation method according to JIS M-8511. As a measuring device, for example, a specific surface area measuring device SS-100 manufactured by Shimadzu Corporation can be preferably used. If the average particle size is larger than 7.0 μm, for example, when a sheet-shaped insulator is formed, depending on the thickness of the insulator layer, the heavy calcium carbonate powder protrudes from the surface and falls off. Otherwise, the surface properties, mechanical strength, etc. may be impaired. In particular, the particle size distribution preferably does not contain powder (particles) having a particle size of 45 μm or more. On the other hand, if the particles are too fine, the viscosity will increase significantly when kneaded with the above-mentioned resin, which may make it difficult to manufacture the insulator. Such a problem can be prevented by setting the average particle size of the inorganic powder to 0.7 μm or more and 7.0 μm or less, particularly 0.8 μm or more and 6.0 μm or less.

In the present invention, the heavy calcium carbonate powder contains at least two groups of particles having different average particle sizes, and the at least two groups of particles having different average particle sizes are air according to JIS M-8511. A first calcium carbonate particle group having an average particle size of 0.7 μm or more and less than 2.2 μm by a permeation method, and a second calcium carbonate particle group having an average particle size of 2.2 μm or more and 7.0 μm or less by an air permeation method according to JIS M-8511. and calcium carbonate particles at a mass ratio of 1:1 to 5:1. As a result, physical properties such as the surface properties of the insulator and the printability and blocking properties can be improved. In addition, uneven distribution of calcium carbonate is suppressed, an insulator having good appearance and mechanical properties such as elongation at break can be obtained, and falling off of calcium carbonate from the insulator can be reduced.

Although not particularly limited, when the average particle size of the first calcium carbonate particle group is a and the average particle size of the second calcium carbonate particle group is b, the a/b ratio is 0.85 or less, It is desirable to be able to classify roughly so that it is more preferably about 0.10 to 0.70, and still more preferably about 0.10 to 0.50. This is because a particularly excellent effect can be expected by jointly using particles having such a clear difference in average particle size to some extent. Further, each of the first calcium carbonate particle group and the second calcium carbonate particle group preferably has a coefficient of variation (Cv) of the distribution of the particle size (μm) of about 0.01 to 0.10, particularly 0 It is desirable to be about 0.03 to 0.08. If the variation in particle size defined by the coefficient of variation (Cv) is this level, it is considered that each powder group can provide more complementary effects. Three or more calcium carbonate groups having different average particle size distributions may be used. Moreover, it is preferable that each of the powders of the first calcium carbonate particle group and the second calcium carbonate particle group is surface-treated ground calcium carbonate.

In the flexible flat cable of the present invention, the insulator contains the heavy calcium carbonate powder as described above, and may further contain inorganic substance powder other than these. Examples include powdery carbonates, sulfates, silicates, phosphates, borates, oxides, or hydrates thereof of calcium, magnesium, aluminum, titanium, iron, zinc, etc. Specifically, for example, light calcium carbonate, magnesium carbonate, zinc oxide, titanium oxide, silica, alumina, clay, talc, kaolin, aluminum hydroxide, magnesium hydroxide, aluminum silicate, magnesium silicate, calcium silicate, Aluminum sulfate, magnesium sulfate, calcium sulfate, magnesium phosphate, barium sulfate, silica sand, carbon black, zeolite, molybdenum, diatomaceous earth, sericite, shirasu, calcium sulfite, sodium sulfate, potassium titanate, bentonite, wollastonite, dolomite, Graphite etc. are mentioned. These may be synthetic or derived from natural minerals, and may be contained singly or in combination of two or more.

Considering the physical properties of the obtained FFC and the moldability of the insulator, the inorganic powder in the insulator is preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably substantially free of unavoidable impurities. Virtually the entire amount consists of the ground calcium carbonate powder described above. In addition, when the insulator constituting the present invention contains an inorganic substance powder other than the heavy calcium carbonate powder, it preferably contains an inorganic substance powder having a dielectric constant of 5 or less, further 4 or less, particularly 3 or less. . Calcium carbonate has a dielectric constant of about 1.6, which is a considerably low dielectric constant among inorganic substances. If the insulator does not substantially contain inorganic substance powders other than heavy calcium carbonate powder, physical properties such as high-frequency characteristics and mechanical characteristics will be particularly good.

<Resin composition>
The insulator constituting the flexible flat cable of the present invention is made of a resin composition containing a polyolefin resin and an inorganic substance powder such as heavy calcium carbonate powder. In the resin composition, the polyolefin resin and heavy calcium carbonate powder are contained in a mass ratio of 50:50 to 10:90. If the content of the heavy calcium carbonate powder is too small, it will be difficult to obtain physical properties such as the texture and strength of the insulator (coating material). .

Moreover, the ratio of the inorganic substance powder, particularly the ratio of the heavy calcium carbonate powder, to the total mass of the resin composition is preferably 52% by mass or more, more preferably 55% by mass or more. The upper limit of the ratio is preferably 80% by mass or less, more preferably 75% by mass or less, and particularly preferably 70% by mass or less.

If necessary, other additives may be added as auxiliary agents to the resin composition that constitutes the insulator. Other additives include, for example, colorants, lubricants, coupling agents, fluidity modifiers (fluidity modifiers), cross-linking agents, dispersants, antioxidants, ultraviolet absorbers, flame retardants, stabilizers, and electrifying agents. Inhibitors, foaming agents, plasticizers, etc. may be blended. These additives may be used alone or in combination of two or more. Moreover, these may be blended in the kneading step described later, or may be blended in the raw material components in advance before the kneading step.

In the resin composition constituting the insulator, the addition amount of these other additives is not particularly limited as long as it does not impede the desired physical properties and workability, but the mass of the entire resin composition is 100%. In this case, each of these other additives is blended in a ratio of about 0 to 10% by mass, particularly about 0.04 to 5% by mass, and the total amount of the other additives is 10% by mass or less. is desired. For example, 10 to 45% by mass, particularly 20 to 25% by mass of polyolefin resin; 90 to 45% by mass, particularly 75 to 55% by mass of heavy calcium carbonate powder; and 0 to 10% by weight, especially 0.04 to 5% by weight of the above additives may be contained.

Among these additives, those considered to be important will be described below by way of examples, but the additives are not limited to these.

Examples of plasticizers include triethyl citrate, acetyl-triethyl citrate, dibutyl phthalate, diaryl phthalate, dimethyl phthalate, diethyl phthalate, di-2-methoxyethyl phthalate, dibutyl tartrate, and o-benzoylbenzoic acid. Ester, diacetin, epoxidized soybean oil and the like. These plasticizers are usually blended in about several mass % with respect to the thermoplastic resin, but the amount is not limited to these ranges. is also possible. However, in the insulator constituting the FFC of the present invention, the blending amount is preferably about 0.5 to 10 parts by weight, particularly about 1 to 5 parts by weight, per 100 parts by weight of the thermoplastic resin.

As the colorant, any of known organic pigments, inorganic pigments, or dyes can be used. Specifically, organic pigments such as azo-based, anthraquinone-based, phthalocyanine-based, quinacridone-based, isoindolinone-based, diosazine-based, perinone-based, quinophthalone-based, and perylene-based pigments, ultramarine blue, titanium oxide, titanium yellow, and iron oxide. (Rouge), chromium oxide, zinc white, carbon black and other inorganic pigments.

Examples of lubricants include fatty acid-based lubricants such as stearic acid, hydroxystearic acid, complex stearic acid, and oleic acid; fatty alcohol-based lubricants; stearamide, oxystearamide, oleylamide, erucylamide, ricinolamide, behenamide, and methylol. Aliphatic amide-based lubricants such as amides, methylenebisstearamide, methylenebisstearobehenamide, higher fatty acid bisamic acids, complex amides; n-butyl stearate, methyl hydroxystearate, polyhydric alcohol fatty acid esters, Fatty acid ester-based lubricants such as saturated fatty acid esters and ester-based waxes; and fatty acid metal soap-based lubricants such as zinc stearate and magnesium stearate.

Phosphorus-based antioxidants, phenol-based antioxidants, and pentaerythritol-based antioxidants can be used as antioxidants. Phosphorus-based, more specifically phosphorus-based antioxidant stabilizers such as phosphites and phosphates are preferably used. Examples of phosphites include triphenyl phosphite, trisnonylphenyl phosphite, tris(2,4-di-t-butylphenyl) phosphite, and other phosphorous acid triesters, diesters, and monoesters. is mentioned.

Phosphate esters include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris(nonylphenyl) phosphate, 2-ethylphenyl diphenyl phosphate and the like. These phosphorus-based antioxidants may be used alone, or two or more of them may be used in combination.

Phenolic antioxidants include α-tocopherol, butylhydroxytoluene, sinapyl alcohol, vitamin E, n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2- t-butyl-6-(3'-t-butyl-5'-methyl-2'-hydroxybenzyl)-4-methylphenyl acrylate, 2,6-di-t-butyl-4-(N,N-dimethyl aminomethyl)phenol, 3,5-di-t-butyl-4-hydroxybenzylphosphonate diethyl ester, and tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxymethyl]methane etc., and these can be used alone or in combination of two or more.

Although the flame retardant is not particularly limited, for example, halogen-based flame retardants or non-phosphorus-based halogen-based flame retardants such as phosphorus flame retardants and metal hydrates can be used. Specific examples of halogen flame retardants include halogenated bisphenol compounds such as halogenated bisphenylalkanes, halogenated bisphenyl ethers, halogenated bisphenylthioethers, and halogenated bisphenylsulfones, brominated bisphenol A, bromine Bisphenol-bis(alkyl ether) compounds such as bisphenol S, chlorinated bisphenol A, and chlorinated bisphenol S, and phosphorus-based flame retardants such as aluminum tris(diethylphosphinate) and bisphenol A bis(diphenyl phosphate). , triaryl isopropyl phosphate, cresyl di-2,6-xylenyl phosphate, aromatic condensed phosphate esters, etc., and metal hydrates such as aluminum trihydrate, magnesium hydroxide, combinations thereof, etc. can be exemplified, respectively, and these can be used alone or in combination of two or more. It works as a flame retardant assistant, and can improve the flame retardant effect more effectively. Furthermore, for example, antimony oxides such as antimony trioxide and antimony pentoxide, zinc oxide, iron oxide, aluminum oxide, molybdenum oxide, titanium oxide, calcium oxide, magnesium oxide, etc. can be used in combination as flame retardant aids. .

The foaming agent is mixed or injected into the thermoplastic resin composition in a molten state in a melt-kneader, and undergoes a phase change from solid to gas, liquid to gas, or gas itself. Used to control the porosity (expansion ratio) of the insulator. A foaming agent that is liquid at room temperature undergoes a phase change to a gas depending on the resin temperature and dissolves in the molten resin, while a foaming agent that is gas at room temperature does not undergo a phase change and dissolves in the molten resin as it is. The foaming agent dispersed and dissolved in the molten resin expands inside the sheet as the pressure is released when the molten resin is extruded into a sheet from an extrusion die, forming a large number of fine closed cells within the sheet and foaming. A sheet is obtained. The foaming agent secondarily acts as a plasticizer that lowers the melt viscosity of the raw material resin composition, and lowers the temperature for making the raw resin composition plasticized.

Examples of blowing agents include aliphatic hydrocarbons such as propane, butane, pentane, hexane and heptane; alicyclic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane; chlorodifluoromethane, difluoromethane, trifluoromethane, trichlorofluoromethane; Methane, dichloromethane, dichlorofluoromethane, dichlorodifluoromethane, chloromethane, chloroethane, dichlorotrifluoroethane, dichloropentafluoroethane, tetrafluoroethane, difluoroethane, pentafluoroethane, trifluoroethane, dichlorotetrafluoroethane, trichlorotrifluoroethane , tetrachlorodifluoroethane and perfluorocyclobutane; inorganic gases such as carbon dioxide, nitrogen and air; and water.

As the foaming agent, for example, a carrier resin containing an active ingredient of the foaming agent can be preferably used. Examples of carrier resins include crystalline olefin resins. Among these, crystalline polypropylene resins are preferred. Moreover, hydrogen carbonate etc. are mentioned as an active ingredient. Among these, hydrogen carbonate is preferred. A blowing agent concentrate containing a crystalline polypropylene resin as a carrier resin and a hydrogen carbonate as a thermally decomposable blowing agent is preferred.

The content of the foaming agent contained in the foaming agent in the molding process can be appropriately set according to the amount of the polyolefin resin and heavy calcium carbonate powder, etc., and is 0.04 to 0.04 with respect to the total mass of the resin composition. A range of 5.00% by mass is preferred.

Various commonly used fluidity modifiers can also be used. Examples include, but are not limited to, peroxides such as dialkyl peroxides such as 1,4-bis[(t-butylperoxy)isopropyl]benzene and the like. Depending on the type of polyolefin resin used, these peroxides also act as cross-linking agents. In particular, when the polyolefin resin has diene-derived structural units, part of the copolymer is crosslinked by the action of the peroxide, which helps control the physical properties and workability of the thermoplastic resin composition. obtain. The amount of the peroxide to be added is not particularly limited, but it is preferably in the range of 0.04 to 2.00% by mass, particularly 0.05 to 0.50% by mass, based on the total mass of the resin composition. .

<Method for preparing resin composition>
As a method for preparing the above resin composition, a conventional method can be used, and the method can be appropriately set according to the molding method (extrusion molding, injection molding, vacuum molding, etc.). For example, it can be prepared by melt-kneading a polyolefin resin and heavy calcium carbonate powder. Melt-kneading is preferably carried out by applying a high shear stress while dispersing each component uniformly. As a mixing device, various devices such as a general extruder, a kneader, and a Banbury mixer can be used. The prepared thermoplastic resin composition can, for example, be formed into pellets of desired shape and size and used to manufacture insulators. Further, depending on the desired shape of the insulator, it is also possible to knead each raw material to prepare a thermoplastic resin composition and at the same time to mold the insulator. For example, a sheet-shaped or tape-shaped insulator (coating material) can be produced by kneading various raw materials with a twin-screw extruder and extruding a sheet-shaped material.

<Insulator manufacturing method>
The method for producing the insulator constituting the flexible flat cable of the present invention is not particularly limited as long as it can be molded into a desired shape, and conventionally known extrusion molding, injection molding, vacuum molding, blow molding, calendar molding, etc. Any method may be used. Furthermore, even in the embodiment in which the insulator is a foam, conventionally known liquid phase foaming methods such as injection foaming, extrusion foaming, foam blowing, etc., as long as they can be molded into a desired shape, or, for example, bead foaming, batch foaming, etc. Any of solid-phase foaming methods such as foaming, press foaming, normal pressure secondary foaming, etc. can be used. In one embodiment of the resin composition containing the crystalline polypropylene as the carrier resin and the hydrogen carbonate as the thermally decomposable foaming agent, an injection foaming method and an extrusion foaming method can be desirably used. Among these, the extrusion molding method is preferred.

Although the extrusion method is not particularly limited, it is preferable to use a twin-screw extruder, particularly a T-die type twin-screw extruder, in consideration of the smoothness of the tape-shaped insulator surface. Using such a molding machine, for example, the melting point of the polyolefin resin + 55 ° C. or less, preferably the melting point of the polyolefin resin or more and the melting point + 55 ° C. or less, more preferably the melting point of the polyolefin resin + 10 ° C. or more and the melting point of the polyolefin resin By extruding at a temperature of +45° C. or less, an insulator with excellent appearance and physical properties can be produced.

The insulator extruded as described above is preferably then subjected to a drawing process. The stretching treatment is not particularly limited, and the film can be stretched uniaxially, biaxially, or multiaxially (such as by tubular stretching) during or after molding. More preferably, it is uniaxially or biaxially stretched (for example, longitudinally and/or laterally stretched). Moreover, the draw ratio is preferably 1.1 times or more and 10.0 times or less, particularly 1.5 times or more and 5.0 times or less. In the case of biaxial stretching, sequential biaxial stretching or simultaneous biaxial stretching may be used. Such a stretching treatment can improve the mechanical properties of the insulator and facilitate adjustment of the dielectric constant and dielectric loss tangent to appropriate values. In addition, the resin composition containing the heavy calcium carbonate powder can be stretched to form minute voids, and as a result, it is possible to reduce the weight of the resin composition. The porosity of the insulator can also be adjusted by blending the foaming agent described above.

<High frequency characteristics of insulator>
The insulator produced as described above generally exhibits excellent high-frequency characteristics, and has a dielectric constant ε of 5 or less and a dielectric loss tangent tan δ of 1×10 ⁻³ or less at a frequency of 1 GHz or higher and at a temperature of 25° C. . The insulator constituting the flexible flat cable of the present invention has a dielectric constant ε of 5 or less, preferably 3 or less at a frequency of 1 GHz or higher and a temperature of 25 ° C. as described above, and a dielectric loss tangent tan δ of 1 × 10 ^-3 . Below, preferably 7×10 ⁻⁴ or less, more preferably 5×10 ⁻⁴ or less, further preferably 4×10 ⁻⁴ or less, particularly preferably 3×10 ⁻⁴ or less, exhibit excellent high frequency characteristics. Moreover, since polyolefin-based resin and heavy calcium carbonate powder are used as main raw materials, it has good mechanical properties and is advantageous in terms of cost.

There are no particular restrictions on the shape and configuration of the insulator, and it can be of any desired shape and configuration according to the intended FFC. In particular, the insulator has a thickness of 20 μm or more and 1000 μm or less, particularly 50 μm or more and 500 μm or less, and a stretching ratio of 1.1 times or more and 10.0 times or less, particularly 1.5 times or more and 5.0 times or less Uniaxially or biaxially stretched Sheets are preferred. A desired shape can be obtained by cutting out a tape-shaped insulator from such a sheet.

The insulator constituting the flexible flat cable of the present invention also preferably has a porosity of 5% or more and 35% or less, particularly 10% or more, further preferably 15% or more and 30% or less. If the insulator contains fine voids at such a ratio, the dielectric constant and the dielectric loss tangent may decrease. Here, the porosity can be calculated from the density (specific gravity) of the insulator. For example, in the case of a sheet made of polypropylene resin and calcium carbonate, the true specific gravity ρ _o of the mixture is calculated from the blending amount using the respective true specific gravities of 0.90 and 2.71. Based on the ratio of that value and the specific gravity ρ of the actual insulator, the porosity can be calculated according to the following formula.
Porosity (volume%) = (1-ρ/ρ _o ) × 100

The porosity and size of the voids in the insulator can be adjusted, for example, by stretching. When a thermoplastic resin composition containing an inorganic substance powder such as a heavy calcium carbonate powder is stretched, the inorganic particles are used as nuclei for stretching, resulting in large voids. It is also possible to adjust the porosity by adding the foaming agent described above. The porosity can also be adjusted by extrusion molding without adding a foaming agent or performing the stretching step. Air entrained in the extruder is usually vented out of the molding machine, but part of it may be caught in the thermoplastic resin composition and form fine voids. Therefore, it is possible to adjust the porosity of the insulator within the above range by examining the extrusion molding conditions.

≪Structure of Flexible Flat Cable≫
In the flexible flat cable of the present invention, a plurality of conductors are arranged inside the insulating covering material as described above. Therefore, the FFC of the present invention has excellent high-frequency characteristics and can transmit signals at high speed with low loss. In a preferred embodiment of the FFC of the present invention, as shown in FIG. 2, a plurality of conductors 13 are interposed between coating materials 11 and 12 made of tape-shaped insulators with an adhesive layer 14 interposed therebetween. are arranged in parallel at predetermined intervals. As described above, the FFC of the present invention may have a structure in which three or more insulator layers are provided and two or more rows of a plurality of conductors are stacked via the insulator layers. In that case, the plurality of insulator layers may have the same shape, such as thickness, and may have different materials.

<Adhesive layer>
As described above, the flexible flat cable of the present invention preferably has an adhesive layer inside the tape-like covering material. The material used for the adhesive layer is not particularly limited, and various known adhesive materials can be used. Examples include polyester-based adhesives, polyamide-based adhesives, epoxy-based adhesives, polyurethane-based adhesives, polyolefin-based adhesives, polyvinyl chloride-based adhesives, terpene-based adhesives, phenolic resin-based adhesives, elastomer-based adhesives, Examples include, but are not limited to, styrene-butadiene copolymers, hydrides such as SEBS, natural rubber, chloroprene rubber, and nitrile-butadiene copolymers. A plurality of adhesives can also be used together. Preferably, a hydrocarbon-based polymer-based adhesive with a low dielectric constant, such as a polyolefin adhesive, a styrene-butadiene copolymer, or the like, is used. Specific examples of polyolefin adhesives include various modified polypropylene grafted with maleic anhydride, epoxidized polypropylene, maleic anhydride-modified polyethylene, amine-modified polyethylene, epoxidized polyethylene, maleic anhydride-modified ethylene-propylene copolymer, Ethylene-vinyl acetate copolymers, ethylene-(meth)acrylic acid ester copolymers and the like can be mentioned, but are not limited to these. Styrene-butadiene copolymers also include, but are not limited to, random copolymers (SBR), block copolymers (SBS), styrene-isoprene copolymers (SIS), and their hydrides such as SEBS. Modified polyolefin-based adhesives are particularly preferred.

Various additives such as flame retardants, antioxidants, plasticizers, etc. may be added to the adhesive layer as desired. In particular, the flame retardant is preferably contained in the adhesive layer in order to make the FFC flame-retardant. As the additive to the adhesive layer, for example, those mentioned above as additives to the resin composition for insulators can be used. However, it is preferable to refrain from using some of the typical flame retardants, such as antimony oxide and titanium oxide, because even a small amount of addition greatly increases the dielectric constant. Preferably, a substance having a dielectric constant of 5 or less, more preferably 3 or less, particularly 2 or less, such as calcium carbonate, talc, clay, or the like is used. Since these flame retardants do not generate harmful gases when heated, they are also suitable from the standpoint of safety.

The amount of the flame retardant compounded is also not particularly limited, and can be arbitrarily selected according to the type of adhesive polymer to be used and the intended physical properties of the FFC. For example, calcium carbonate or talc may be added to the polyolefin adhesive or ethylene-vinyl acetate copolymer in an amount of 5 to 70% by weight, further 10 to 60% by weight, particularly 20 to 40% by weight. In the FFC of the present invention, flame retardancy is ensured by a large amount of heavy calcium carbonate in the coating material, so there is no need to blend a large amount of flame retardant such as antimony oxide in the adhesive layer. The FFC of the present invention having the insulator described above has the advantage of easily exhibiting excellent high-frequency characteristics from this point of view as well.

<Other parts>
If desired, the flexible flat cable of the present invention may be provided with a reinforcing layer, an armor layer, or the like. Also, a shield layer may be provided on the outside in order to prevent the influence of external noise. The type of reinforcing layer is not particularly limited, and for example, a polymer layer containing polyethylene fiber, polypropylene fiber, glass fiber, or the like can be used. The type of shield layer is also not limited, and for example, a laminate of aluminum foil and polymer can be used. In order to ensure the high-frequency characteristics of the FFC of the present invention, the polymer in the shield layer is preferably a resin mainly composed of hydrocarbons, particularly a polyolefin resin such as modified polypropylene.

The FFC of the present invention configured as described above has excellent high-frequency characteristics and can transmit signals at high speed with low loss. The FFC of the present invention is flexible and easy to handle, has excellent mechanical properties, and is advantageous in terms of cost because the base polymer of the covering material is a polyolefin resin. In addition, since a large amount of heavy calcium carbonate is blended in the coating material, it is also excellent in flame retardancy.

The present invention will be described in more detail below based on examples. It should be noted that these Examples are intended to provide specific aspects and embodiments in order to facilitate an understanding of the concept and scope of the present invention disclosed herein and recited in the appended claims. For illustrative purposes only, the present invention is in no way limited to these examples.

In the following examples, various insulators were prepared from the following raw materials, and flexible flat cables were produced using these insulators as coating materials. The FFC, the raw material, and the insulator thus produced were evaluated for their characteristics as follows.

(Average particle size of inorganic substance powder)
Using a specific surface area measuring device SS-100 manufactured by Shimadzu Corporation, it was calculated from the results of measuring the specific surface area by the air permeation method in accordance with JIS M-8511.

(Specific surface area of inorganic substance powder)
Using BELSORP-mini manufactured by Microtrac BELL, it was determined by the nitrogen gas adsorption method.

(Roundness of inorganic powder)
100 particles are sampled so as to represent the particle size distribution of the powder, and the projection of each particle obtained using an optical microscope is image analyzed using commercially available image analysis software. asked for As the measurement principle, the projected area and the projected perimeter of the particle are measured and defined as (A) and (PM), respectively. Let (B) be the area of a circle with the same perimeter as the projected perimeter of
Roundness=A/B=A×4π/(PM) ²
is a request.

(Tensile properties of insulator)
Tensile strength and elongation at break were measured using Autograph AG-100kNXplus (Shimadzu Corporation) under conditions of 23° C. and 50% RH in accordance with JIS K 7161-2:2014. A dumbbell-shaped test piece was cut out from a molded product described later. The drawing speed was 50 mm/min.

(Electrical properties of insulator)
Permittivity and dielectric loss tangent were measured at 25° C. using a cavity resonator at a frequency of 1 GHz in accordance with JIS 2565.
The volume resistivity was measured in accordance with JIS K 6921-2:2018 using a resistivity meter MCP-HT800 manufactured by Nitto Seiko Analyticc Co., Ltd.

(Signal transmission characteristics of FFC)
Each FFC specimen was used as an image signal cable for a liquid crystal display, and an image test using an SMPTE color bar was performed. After warming up the monitor, the brightness was adjusted so that the black +4 IRE bars of the PLUGE signal were visible and the black -4 IRE bars were not visible. Next, the gain was adjusted so that the white of the 100% white bar was not crushed. Further, the monitor was set to the Blue-only mode (green and red turned off), and the HUE knob and the SAT knob were adjusted so as to eliminate the luminance difference between the color bar and the inverted color bar, thereby performing color adjustment. After these adjustments, the images were visually observed and evaluated on a 5-point scale, with 5 indicating no distortion or unclear portions, and 1 indicating conspicuous distortion or unclear portions.

(raw materials)
Raw materials used in the following examples and comparative examples were as follows.
- Thermoplastic resin PP: polypropylene homopolymer (manufactured by Prime Polymer Co., Ltd.: Prime Polypro (registered trademark) E111G, melting point 160 ° C.)

・Inorganic substance powder CC1: heavy calcium carbonate particles (no surface treatment), average particle diameter 1.10 μm, specific surface area 32,000 cm ² /g, circularity: 0.55
CC2: Heavy calcium carbonate particles (no surface treatment) Average particle size 3.60 µm, specific surface area 6,000 cm2/g, circularity: 0.90
CC3: Heavy calcium carbonate particles (no surface treatment) Average particle diameter 2.2 μm, specific surface area 10,000 cm ² /g, circularity: 0.85
CC4: Heavy calcium carbonate particles (fatty acid surface treatment) Average particle diameter 2.2 μm, specific surface area 10,000 cm ² /g, circularity: 0.85
MgO: Magnesium oxide fine particles, average particle size 0.2 μm

・ Additive D (antistatic agent): PC-4 (lithium salt) manufactured by Marubishi Yuka Kogyo Co., Ltd.
E (lubricant): magnesium stearate F1 (antioxidant): Adekastab (registered trademark) AO-60 (phenolic antioxidant) manufactured by ADEKA Co., Ltd.
F2 (antioxidant): Adekastab (registered trademark) 2112 (phosphite antioxidant) manufactured by ADEKA Co., Ltd.

・ Adhesive AD: Maleic anhydride-modified polypropylene resin

[Example 1]
(Preparation of insulator sheet)
Among the above raw materials, 40 parts by mass of PP, 40 parts by mass of CC1, 20 parts by mass of CC2, and 1 part by mass each of additives D, E, F1, and F2 were mixed with a co-rotating machine manufactured by Parker Corporation. The mixture was put into a twin-screw kneading extruder HK-25D (φ25 mm, L/D=41), extruded into strands at a cylinder temperature of 190 to 200° C., cooled, and cut into pellets.

The pellets prepared as described above are extruded at 220°C by a Laboplastmill single-screw T-die extruder (φ20 mm, L/D = 25) manufactured by Toyo Seiki Seisakusho Co., Ltd., so that the pellets are 4 times larger in the take-up direction. Then, it was stretched at 190° C. to form a sheet having a thickness of about 150 μm. The resulting insulator sheet was evaluated for tensile properties and electrical properties by the above test methods. The evaluation results are shown in Table 1 below together with the blending of raw materials and moldability.

(Preparation of FFC)
One surface of the insulating sheet obtained as described above was extrusion-coated with the adhesive AD to a thickness of about 300 μm using a T-die extruder to obtain an insulating base material. Next, 10 tin-plated flat annealed copper conductors with a thickness of 35 μm and a width of 0.3 mm are sandwiched in parallel at a pitch of 0.5 mm between an insulating base material prepared in the same manner, and passed through a heat roller. They were laminated and integrated to form an FFC test body.

[Examples 2 to 4, Comparative Examples 1 to 3]
Insulator sheets and FFC specimens were produced and evaluated in the same manner as in Example 1, except that the composition of the insulator sheet and the stretching method were changed as shown in Table 1. Evaluation results and the like are shown in Table 1 below.

[Comparative Example 4]
The same method as in Example 1 was used to evaluate the signal transmission characteristics of a commercially available FFC. An analysis of the coating material of the FFC used revealed that the base polymer was PET. Evaluation results are shown in Table 1 below.

According to the present invention, a polyolefin resin and a heavy calcium carbonate powder are contained in a mass ratio of 50:50 to 10:90, and the dielectric constant ε at 1 GHz / 25 ° C. is 5 or less and the dielectric loss tangent tan δ is 5 × All of the FFCs of Examples 1 to 4, which are coated with tape-shaped insulators of 10 ⁻⁴ or less, exhibited good signal transmission characteristics at frequencies in the 2.45 GHz band. In particular, Example 1, in which two groups of heavy calcium carbonate powders having different average particle sizes were blended, and Example 4, in which surface-treated heavy calcium carbonate powder was blended, exhibited extremely good signal transmission characteristics. On the other hand, the FFCs of Comparative Examples 1 to 3 made from insulators containing no or a small amount of heavy calcium carbonate, and the commercially available FFC of Comparative Example 4 having a PET resin as a coating material, have problems in signal transmission. did.

Moreover, in Examples 1 to 4 according to the present invention, the insulator sheets not only exhibited good dielectric constant and dielectric loss tangent, but were also excellent in formability and tensile properties. In particular, in Example 1, in which two groups of ground calcium carbonate powders having different average particle sizes were blended, and in Example 4, in which surface-treated ground calcium carbonate powder was blended, such an advantage was remarkable. It has been found that the FFC according to the invention combines excellent signal transmission properties with good mechanical properties.

[Example 5]
The same operation as in Example 1 was performed, except that 40 parts by weight of PP, 60 parts by weight of CC4, and 1 part by weight each of additives E, F1, and F2 were used as raw materials. Evaluation results and the like are shown in Table 2 below.

[Example 6]
The same operation as in Example 5 was performed, except that the uniaxial stretching was not performed. Evaluation results and the like are shown in Table 2 below.

[Example 7]
The same procedure as in Example 5 was followed, except that the sheet was not stretched after extrusion, but was instead vacuum pressed to form a sheet with a thickness of about 220 μm. Evaluation results and the like are shown in Table 2.

Examples 5 and 6 showed that the stretching operation improved the high-frequency characteristics of the insulator and the signal transmission characteristics of the FFC. Further, from Example 7, it was shown that if the porosity is less than 5%, the signal transmission characteristics may be slightly inferior to the FFC having the insulator with the same formulation but different porosity.

As shown in the above examples, the present invention provides a flexible flat cable that has both good signal transmission characteristics and mechanical characteristics and that can transmit signals at high speed with low loss. The flexible flat cable of the present invention is advantageous in terms of cost because the insulator, which is a constituent material, is mainly composed of polyolefin resin and heavy calcium carbonate powder.

1 flexible flat cable 11 covering material (insulator)
12 Coating material (insulator)
13 conductor 14 adhesive layer

Claims (7)

A flexible flat cable in which a plurality of conductors are arranged in parallel at predetermined intervals inside a covering material made of a tape-shaped insulator,
The insulator contains polypropylene homopolymer and heavy calcium carbonate powder at a mass ratio of 50:50 to 10:90, and has a dielectric constant ε of 5 or less at a frequency of 1 GHz and a temperature of 25 ° C. , the dielectric loss tangent tan δ is 5 × 10 ^-4 or less ,
The resin component contained in the insulator is composed of a polypropylene homopolymer,
Flexible flat cable. The flexible flat cable according to claim 1, wherein the ground calcium carbonate powder is surface-treated ground calcium carbonate powder. 3. The flexible flat cable according to claim 1, wherein the heavy calcium carbonate powder has an average particle size of 0.7 μm or more and 7.0 μm or less as measured by an air permeation method according to JIS M-8511. The heavy calcium carbonate powder has a BET specific surface area of 0.1 m ² /g or more and 10.0 m ² /g or less , and a circularity of 0.50 or more and 0.95 or less. The flexible flat cable described in . The heavy calcium carbonate powder contains at least two groups of particles having different average particle sizes, and the at least two groups of particles having different average particle sizes are averaged by an air permeation method according to JIS M-8511. A first calcium carbonate particle group having a particle size of 0.7 μm or more and less than 2.2 μm, and a second calcium carbonate particle group having an average particle size of 2.2 μm or more and 7.0 μm or less measured by an air permeation method according to JIS M-8511. and in a mass ratio of 1: 1 to 5: 1,
The flexible flat cable according to any one of claims 1-4 . 6. The a/b ratio is 0.85 or less, where a is the average particle size of the first calcium carbonate particle group and b is the average particle size of the second calcium carbonate particle group. flexible flat cable. The flexible flat cable according to any one of claims 1 to 6 , wherein said insulator has a porosity of 5% or more and 35% or less.

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